A bow is a simple machine in which the limbs define a two-arm spring. The energy stored by the archer is in form of the drawn stressed bow. The potential energy is then transferred to the arrow in the form of kinetic energy when the archer releases the bowstring permitting the bow limbs to spring forward.
An arrow consists of a tip which may be a target point type or a broadhead type which is affixed to one end of a shaft which may be composed of wood, fiberglass, metal or other suitable material, a nock for resting against a bowstring, and finally fletching, also known as fins or vanes affixed upon the shaft just ahead of the nock for purposes of aerodynamic stabilization during flight. Among the several factors affecting the distance an arrow flies are the initial angle, the initial velocity, arrow weight, the length of the arrow, and the relative surface area of the arrow fletching.
Spin influences directional stability which is the stability of a moving body about an axis. Drag stability is directional stability produced by the fletching on the arrow shaft. Rate of spin is determined by the vane geometry about the arrow shaft and more specifically to the fletching scheme. Fletching can be straight, offset or helically oriented. Both offset and helical configurations will cause the shaft to spin with a helical configuration producing the highest rate of spin.
When preparing to shoot an arrow, the nock of the shaft is temporarily mounted to the bow string which is drawn back deforming the bow.
Conventional nocks, being fixed to the end of the arrow shaft and necessarily rotating with the arrow shaft, prevent the arrow shaft from assuming a spin while the bowstring is engaged with the nock during the initial release phase of the arrow. It is only after the nock separates from the bowstring that a natural spin can begin to occur. A conventional nock (1) robs the arrow of energy by immobilizing the arrow shaft and accelerating non-spinning fletching forward causing increased air resistance producing drag on the arrow, and (2) interferes with early stabilization that would occur at the onset of release if the arrow were somehow permitted to begin spinning upon release.
What is needed is a nock assembly that permits free rotation of the fletching immediately upon release by not impeding the natural rotation of the shaft imparted by the fletching configuration moving through the air. Such as nock would (1) reduce wind resistance by allowing the fletching to promote a natural spin of the arrow immediately upon release, (2) increase stabilization of the shaft by allowing earlier spin and (3) eliminate string torque which is caused by the non-uniform forces present when those surfaces of a fixed nock contacting the bowstring are forced angularly against the bowstring at release because of the natural tendency of the fletching that wants to begin spinning upon release. Because the nock is radially torqued against the bowstring by the rotational tendencies of the fletching acting on the shaft, the torquing slightly readjusts the path of the arrow shaft at that moment in time where the nock and the bowstring actually separate. Finally, for at least the reasons given above, a nock permitting the free rotation of an arrow shaft while still contacting a bowstring would, assuming the same shooter and gear, provide a relatively greater degree of precision.